In this flawed mystery-thriller from flamboyant horror director Dario Argento, Karl Malden portrays a blind man who joins forces with a reporter (James Franciscus) to catch a killer with an extra chromosome. Much of the action occurs at a research hospital, where the killer seeks to conceal the original crime with still more murders. Easily the least interesting of Argento's early thrillers (which include the superior L'Uccello dalle Piume di Cristallo and Quattro Mosche di Velluto Grigio), this film seems almost a parody of the genre at times, with preposterous coincidences and bogus Freudian analysis substituting for genuine mystery.